You don't need to put anything on it. Cold sores are caused by a virus, the herpes virus, and are spread by contact, such as when saliva or other secretions of the infected person touch another person.

Sometimes children get lots of sores — not just on the lips but inside the mouth as well. Sores inside the mouth can be quite painful, making it hard for some children to drink, so doctors will occasionally prescribe medications to coat the sores and make drinking more comfortable. But for the few sores that appear on or near the lips, nothing is generally recommended, except staying away from acidic or salty foods, which can burn. With a little time and patience, cold sores go away by themselves.

If your child is having a lot of discomfort from the sore, if it has a golden yellow scab, if there is pus inside it, or if your child has a fever, call your doctor. Together you can decide if it truly is a cold sore, and whether any further tests or treatments make sense.